It is notoriously well known in the processing of fluid streams to employ static mixers and heat exchangers as enhancements in promoting product uniformity and adjusting product temperature. Mixers can contain active elements such as paddles and rotors although it is quite common to provide static elements whereby the turbulent flow of the fluids in and around these elements enhance fluid mixing without the need for moving parts which inherently add to the cost of the mixing operation both in terms of power requirements and labor intensive maintenance procedures. Many static mixers rely on a mixing element configuration that presents a set of interstices to the product flow. Elements of this type divide a fluid stream along the mixing path and recombine locally created sub streams into a more homogeneous mixture.
It is further common to contain within a conduit a series of tubes or pipes to effect heat transfer between a product stream and a fluid medium contained within tubes in contact with the flow of fluid product.
It has long been known that reduction of the internal film coefficient of the moving fluid product as it contacts the tubes or pipes of a conventional tube and shell heat exchanger is advantageous for reduction of the internal film coefficient enhances heat transfer. In this regard, reference is made to FIG. 1 showing a conventional tube and shell heat exchanger 10. In this configuration, the product enters orifice 13 at the upstream end of the heat exchanger and exits at orifice 14. Heat transfer medium enters the heat exchanger at orifice 16 and travels in a counterflow direction within the heat exchanger to exit at orifice 15. Devices, such as metal strips 17, are frequently installed in the tubes or pipes of such conventional tube and shell heat exchangers in order to enhance the internal film coefficient at its inside tube wall. Such devices can be twisted strips of metal or static or motionless mixers. As noted, the major resistance to heat transfer is due to what is called the “film coefficient” at the inside wall of the tubes where the product velocity is low. The cooling or heating medium flows within tubes 19 while the product travels over the outside of the tubes in area 12. It has been determined that the improvement in heat transfer obtained by tube inserts for laminar flow applications is usually in the range of two to five times. However, the use of such devices significantly increases the pressure drop experienced and thus one using such expedients must pay a price.
FIG. 2 shows yet another conventional device employed as both a heat exchanger and static mixer. Device 20 relies upon a different design concept than the conventional tube and shell heat exchanger of FIG. 1 in that the product of interest is introduced within conduit 23 at upstream end 21 while the cooling/heating medium is contained within tubes 24. It is further noted that the linear tube structure shown as element 11 of FIG. 1 is replaced by tube structure 24 in the form of a static mixer built of tubing instead of sheet metal. However, it has been determined that the device shown in FIG. 2 does not provide a good utilization of the exchanger shell available volume, less, in fact, than the conventional tube and shell tube heat exchanger.
It is thus an object of the present invention to provide a device in which a moving fluid product is both mixed and subject to heat transfer as a result of its contact with a fluid medium employed for that purpose.
It is a further object of the present invention to accomplish the above-referenced objects while, at the same time, improving the efficiency of such a device dramatically as compared to devices offered for this purpose commercially. These and further objects of the present invention will become more readily apparent when considering the following disclosure and claims.